More Details:
Some plugins redirect to some urls containing unicode characters without escaping them first. Escape functions esc_url and esc_url_raw do not solve this either. I think solving this at core level is the best thing to do, especially that it doesn't affect the current behavior of the function.

Change History (3)

When sanitizing a URL to redirect to, UTF-8 characters can be URL encoded, instead of being removed.

While RFC 3986 does not specify which character sets are allowed in URIs, Section 2.5 states that octects matching UTF-8 character encoding should be percent-encoded, then unreserved octets outside of the UTF-8 range should be percent-encoded. As browsers tend to only implement support for UTF-8 in URLs, this change only implements the UTF-8 encoding part. We may revisit the second part if it becomes an issue.